1. Field of the Invention
The present invention relates to a paper feeder that is for picking up paper used in such apparatuses as electro-photographic apparatus, printers, etc. one sheet at a time and feeding pickup paper in a prescribed direction, and an image forming apparatus using this paper feeder.
2. Description of the Related Art
A paper feeder adopting a frictional paper feeding system for taking out paper placed in a paper supply tray in a paper supply cassette or a manual paper supply tray using a friction paper supply member, for example, pickup rollers, separating taken out paper one by one using a separation pad or a separation roller and sending out the paper in the image forming direction is now put in practical use in image forming apparatus widely.
On the other hand, color image formation and high quality image formation of image forming apparatus are in widespread use in recent years and stabilized supply of a large amount of thicker paper and coating paper, etc. is demanded. However, weight (mass per unit area) of such special paper as thicker paper, coating paper is larger than ordinary paper and furthermore, in the case of coating paper, sheets have good smoothness and are closely adhered to each other. Therefore, it becomes difficult to separate special sheets of paper having a highly close adhering force and it was difficult to supply paper stably for conventional pickup rollers that were for frictionally supplying ordinary paper.
Therefore, it was so far a general practice to feed special paper having a high adhering force between sheets of paper by setting paper in a manual paper supply tray one by one using a manual paper feeder in a conventional image forming apparatus.
However, when paper is set in a manual tray one by one, productivity of image formation is low and cannot meet a demand for mass production of a large amount of images at a high speed.
So far, as disclosed in Japanese Patent Application No. 11-171354, an apparatus has been developed to get a stable paper supply by varying pressure force of pickup rollers according to characteristic of using paper.
However, in a conventional paper feeder that varies pressure force of pickup rollers, in case of paper has high adhesion force between paper, when the pressure force of the pickup rollers is increased, this pressure force acts on not only a paper placed on the top but also second and subsequent paper. As a result, the paper adhesion force becomes higher, good separation cannot be obtained and the stable paper feeding is impeded.
When paper with extremely high paper adhesion and thin resin coated on both surfaces for use by color copiers were supplied, separation resisting force caused by adhesion force generated on the overall surface of paper became higher than friction paper supply force by pickup rollers, separation of paper was made difficult and the stable paper feeding was enabled.
Accordingly, when paper with extremely high separation resisting force are supplied by the friction paper supply system, it is demanded to get the stable supply of a large amount of paper at a high speed regardless of kind of paper and is desired to get a paper feeder and an image forming apparatus having high productivity.
An object of the present invention is to feed a large amount of paper at a high speed regardless of kind of paper by increasing a paper feeding capacity of a frictional paper feeding system by making it easy to separate paper having large adhesion force against separation resisting force.
According to the embodiments of the present invention, there is provided a paper feeder comprising: a paper tray; and friction paper supplying members with a total width more than 40% of the maximum paper width supportable by the paper trays for taking out a paper at the top position supported by the paper tray in the prescribed take-out direction.
Further, according to the embodiments of the present invention, there is provided a paper feeder comprising a paper tray to supporting paper and friction paper supplying members that are in parallel with the width direction of the paper supported by the paper tray, divided and arranged on plural shafts for taking out the paper at the top position supported by the paper tray.
In addition, according to the embodiments of the present invention, there is provided an image forming apparatus comprising: a paper supply tray provided in the main body of the apparatus for supporting paper; pickup rollers with a total width more than 40% of the maximum paper width supportable by the paper supply tray; and image forming mechanisms provided in the main body of the apparatus for forming images on the paper taken out by the pickup rollers.
Furthermore, according to the embodiments of the present invention, there is provided an image forming apparatus comprising: a paper supply tray provided in the main body of the apparatus for supporting paper; pickup rollers in parallel with the width direction of the paper supported by the paper supply tray and divided and arranged on plural shafts for taking out a paper at the top position supported by the paper supply tray; and image forming mechanisms provided in the main body of the apparatus for forming images on the paper taken out by the pickup rollers.